The present invention relates to an oil-in-water aqueous emulsion of an organopolysiloxane compound and a method for the preparation thereof. More particularly, the invention relates to an aqueous emulsion of a high-viscosity organopolysiloxane compound of the oil-in-water type having usefulness as an adjuvant ingredient in toiletry preparations for hair-care treatment, polishing agents, mold-release agents, fabric-finishing agents and the like as well as to a method for the preparation of such an oil-in-water aqueous organopolysiloxane emulsion composition.
As is well known, organopolysiloxane compounds in the form of an aqueous emulsion are widely employed as an almost indispensable adjuvant in toiletry preparations for hair-care treatment, polishing agents, mold-release agents, fabric-finishing agents and the like. When an aqueous emulsion of an organopolysiloxane compound is employed as an adjuvant in a toiletry preparation for hair-care treatment, in particular, it is generally preferred that the organopolysiloxane compound has a relatively high viscosity or degree of polymerization in view of good adhesion of the high-viscosity organopolysiloxane compound to the hair as compared with low-viscosity organopolysiloxane compounds. Besides the viscosity of the organopolysiloxane compound, the particle diameter of the organopolysiloxane droplets as emulsified in an aqueous medium is another important parameter having significance on the performance of the toiletry preparation compounded with an aqueous organopolysiloxane emulsion. For example, a formulation of a shampoo composition is proposed in Japanese Patent Kokai 4-36226 and 4-224309 according to which a shampoo composition is admixed with an aqueous emulsion of an organopolysiloxane compound having a droplet diameter smaller than 2 .mu.m in order not to unduly decrease the foamability of the shampoo composition. Further, Japanese Patent Kokai 63-130512, 5-13994 and 5-163122 each teach a method in which an organopolysiloxane compound is added to a hair-care treatment composition in the form of a so-called microemulsion as a much finer dispersion of the organopolysiloxane compound than in ordinary aqueous emulsions of the organopolysiloxane.
The above mentioned aqueous emulsion of an organopolysiloxane compound of which the particle diameter of the emulsion droplets is relatively small has a problem that the adhesive power of the organopolysiloxane droplets to the hair surface is so poor that the organopolysiloxane droplets once deposited on the hair surface are readily washed away by rinsing resulting in the loss of the hair-treatment effect. In this regard, a proposal is made in Japanese Patent Kokai 7-188557 for the use of an aqueous emulsion of an organopolysiloxane compound as an adjuvant to toiletry preparations, of which the organopolysiloxane droplets have a relatively large diameter in the range from 3 to 100 .mu.m. Since the surface active agent used in the preparation of this organopolysiloxane emulsion is anionic, however, the organopolysiloxane emulsion is not always always suitable as an adjuvant to hair-care treatment compositions such as hair rinses, hair conditioners, hair treatments and the like formulated sometimes with a cationic surface active agent to cause phase separation or formation of precipitates although the organopolysiloxane emulsion is suitable as an adjuvant to a shampoo composition in which the surface active agent is almost always anionic.
In view of the problem of incompatibility of the surface active agents, a proposal is made in Japanese Patent Kokai 9-316331 for the use of a cationic surface active agent such as a quaternary ammonium salt compound in the preparation of an aqueous organopolysiloxane emulsion.
The surface active agent used in the preparation of an aqueous organopolysiloxane emulsion as an adjuvant in hair rinses, hair conditioners and hair treatments is not limited to cationic surface active agents but can be a fatty acid amidoamine salt compound which is compatible with anionic surface active agents. For example, a report is given in Journal of Society of Cosmetic Chemistry of Japan, Notes, volume 31, No. 1, pages 75-78 (1997) on the feasibility of an amphoteric surface active agent in a hair-rinse composition, according to which fatty acid amidoamine salt compounds are advantageous in respect of, besides the compatibility with anionic surface active agents, low irritativeness to the skin, little accumulation on the hair and mild rinsing effect. Although it would be a due idea accordingly to employ a fatty acid amidoamine salt compound as an emulsifying agent in the preparation of an aqueous emulsion of an organopolysiloxane having a high viscosity or degree of polymerization with an object to accomplish further improvements of a hair-care treatment composition relative to the gloss and lubricity of the treated hair and hair-protecting effect under full utilization of the above mentioned various features of the compound, an attempt according to this idea, however, is unsuccessful and a fully stable aqueous emulsion of a high-viscosity or high-polymerization organopolysiloxane compound cannot be obtained due to the relatively low emulsifying activity of fatty acid amidoamine salt compounds in general.